(99m) Tc-anti-cardiac Troponin I Monoclonal Antibody Myocardial Radioimmunoassay Imaging In Basic Research

Objective:1.To explore the methodology of direct labeling of anticardiactroponin I monoclonal antibody (AcTnIMA) with ^99mTc and to investigatethe stability of ^99mTc-AcTnIMA in vitro.2.To study the quantity and time correlation of the clearance of^99mTc-AcTnIMA in the blood of rabbit.3.To study distribution of ^99mTc-AcTnIMA in healthy rats.4.To study the distribution pattern of ^99mTc-AcTnIMA in rats withexperimental myocardial injury, thereby determining the possibility of^99mTc-AcTnIMA to be a tracer of myocardial radioimmunoimaging.Methods:1.AcTnIMA, reduced by SnCl₂, was labeled with ^99mTC. The bestsynthesic condition of the 4 factors—quantity of AcTnIMA and SnCl₂, pHand radioactivity, was screened by orthogonal experimental design. Thelabeling efficiency of the product was measured by paper chromatography,and the purity of ^99mTc-AcTnlMA was determined by columnchromatography. Then the stability of the product was observed at roomtemperature (22°) at 0,2,4,6h.2.Blood samples were collected from the experimental animal at 0,20, 40, 60, 90, 120, 150, 180, 240min after injection of ^99mTc-AcTnIM.Injected dose%/gram (ID %/g) was calculated and a clearance curve wasdrawn accordingly, where the half time of clearance could be determined.3.20 healthy rats, injected with 0.2mci ^99mTc-AcTnIMA, were killedat 2h, 4h, 6h and 8h respectively (5 rats each time). Blood, liver, spleen,kidneys, healthy muscles, lungs and heart were taken and injectiondose%/gram (ID%/g) were calculated.4.110 rats were divided into two groups. Then the first group of 60 rats were divided into experimental group, pharmic control group andblank control group. In the experimental group, 20 rats with acutemyocardial lesion were injected with 0.2mci ^99mTc-AcTnIMA, andkilled 2h, 4h, 6h and 8h after injection respectively (5 rats each time).Blood, liver, spleen, kidneys, healthy muscles, lungs and heart were takenand injection dose%/g (ID%/g) and the ID%/g ratio of heart to lung(HLR) were calculated. In the pharmic control group, 20 rats with acutemyocardial lesion were injected with 0.2mci ^99mTc-N-IgG and were killedin the same way as the experimental group. Lungs and hearts were takenand ID%/g and HLR were calculated. In the blank control group, 20healthy rats, injected with 0.2mci ^99mTc-AcTnIMA, underwent the same 4procedures as the pharmic group. 50 rats of the second group withmyocardial lesion were injected with 0.2mci ^99mTc-AcTnIMA 2h, 4h, 6h,8h, 12h, 24h, 3d, 5d, 10d and 15d after myocardial injury respectively (5rats each time), and killed 4h after injection, and then ID%/g and HLRwere calculated.Results:1.The labeling efficiency was more than 99%, and its bestexperimental condition was described as below: AcTnIMA 30μg, SnCl₂80μg, pH 7 and radioactivity 50mci. Purity of ^99mTc-AcTnIMA in theproduct was fairly high. The labeling efficiency was still above 95% at6h.2.The half time of clearance of blood ^99mTc-AcTnIMA wasapproximately 60min.3.^99mTc-AcTnIMA showed significantly higher distribution inkidneys and livers than any other organs.4.It showed specific uptake of ^99mTc-AcTnIMA by compromisedcardiac muscles with the peak time of 4h, and the uptake had nothing to do with the time after lesion.Conclusion:1.^99mTc direct labeling of AcTnIMA is simple and efficient, and theproduct is of high stability in vitro.2.Clearance of blood ^99mTc-AcTnIMA was quite fast.3.^99mTc-AcTnIMA was excreted mainly in urinary and digestivesystems.4.99mTc-AcTnIMA can hopefully be a tracer of myocardialradioimmunoimaging to diagnose myocardial injury.